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  • How to Wrap or Upgrade a Brushless Outrunner Motor

    I don't know if you saw my post BELOW about doubling dimensions. Other than that, with experience with different motors you can carefully make good educated guesses on different designs. The farther you go from an untested design the farther from reality your estimates will likely be. Otherwise There are probably college textbooks that explain it all, it would take a while to learn with lots of hard math involved. There are CAD programs with simulators that designers and manufacturers use which cost hundreds or more and usually require an expensive class for a few days just to use them let alone learning the math and terminology.With a lot of experience and thinking things through and a little research you can with good accuracy know the performance of a motor you design and build. The ...see more »I don't know if you saw my post BELOW about doubling dimensions. Other than that, with experience with different motors you can carefully make good educated guesses on different designs. The farther you go from an untested design the farther from reality your estimates will likely be. Otherwise There are probably college textbooks that explain it all, it would take a while to learn with lots of hard math involved. There are CAD programs with simulators that designers and manufacturers use which cost hundreds or more and usually require an expensive class for a few days just to use them let alone learning the math and terminology.With a lot of experience and thinking things through and a little research you can with good accuracy know the performance of a motor you design and build. The math helps get performance numbers according to specifications, the experience is important for knowing how your materials will affect things, whether or not you math is accurate, and you could just look at your design and see it's limitations without thinking through much math.

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  • How to Wrap or Upgrade a Brushless Outrunner Motor

    motors's kv and torque is easily estimated with proportions: double length and halve kv and double torque, same for doubling diameter, same for doubling turns, same I think for doubling magnet number. Y vs D termination I don't think has an easy proportion.

    Calculating KV is complicated and is determined by many variables that include efficiency variables. Variables include:exact magnet type and dimensions, number of magnets,magnet to stator air gap, stator material, dimensions and lamination thickness,number of stator slotsfriction from air and bearings, and of course the number of turns, Y vs Delta termination, and wire resistance.Estimates work well though if you have a starting point, so for your motor rewind it the same way as it was made except with 1.6 times the original number of turns if my math is correct. More turns can be compared to more leverage and slower speed since more wire is acting on the magnets if that's a good way to visualize it. I'm no expert on these, so that's my best example. I guess it is kind of like a compoun...see more »Calculating KV is complicated and is determined by many variables that include efficiency variables. Variables include:exact magnet type and dimensions, number of magnets,magnet to stator air gap, stator material, dimensions and lamination thickness,number of stator slotsfriction from air and bearings, and of course the number of turns, Y vs Delta termination, and wire resistance.Estimates work well though if you have a starting point, so for your motor rewind it the same way as it was made except with 1.6 times the original number of turns if my math is correct. More turns can be compared to more leverage and slower speed since more wire is acting on the magnets if that's a good way to visualize it. I'm no expert on these, so that's my best example. I guess it is kind of like a compound pulley system where a long wire pulled it's length moves the output end of the pulleys a certain distance, but it takes a wile to pull that whole length of wire and in the mean time the leverage was increased to lift more weight. If you turn the system around so you pull on the output end of the pulleys you pull a very short length of rope and move a very long distance on the output end. So more turns = more torque and lower kv, less turns = less torque and more kv

    biggest factor that determines kv is equally windings magnets and stator dimensions.You are correct on the kvWire diameter has to decrease from the original because more turns means more wire volume, and the stator slots can't hold that, so the diameter has to degrease ideally only enough to keep the slots full or almost full for air to still go through. Smaller diameter wire will decrease torque to the extent that less amps can go in before the motor overheats, so less power can go in. In general motors are limited to a certain power output based on size which is a major cooling ability factor. Because you end up with a lower kv you can use more voltage to still get the same rpm out, using more voltage means you can get more power through the motor before it overheats, in general amps ...see more »biggest factor that determines kv is equally windings magnets and stator dimensions.You are correct on the kvWire diameter has to decrease from the original because more turns means more wire volume, and the stator slots can't hold that, so the diameter has to degrease ideally only enough to keep the slots full or almost full for air to still go through. Smaller diameter wire will decrease torque to the extent that less amps can go in before the motor overheats, so less power can go in. In general motors are limited to a certain power output based on size which is a major cooling ability factor. Because you end up with a lower kv you can use more voltage to still get the same rpm out, using more voltage means you can get more power through the motor before it overheats, in general amps causes most of the heating, but watts contributes, so in the end you shouldn't loose power output. The decreased wire diameter can lower the kv very slightly due to higher resistance, but using higher voltage can help counter that. It will probably be a very small kv drop. Too small of ESC or too weak C rating lipo can affect the kv too, so to find the true kv it is best to use an over sized battery (capacity and discharge rate wise) and ESC and measure the no load rpm at full throttle. Many cheaper motors are not accurately rated just so you know.

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